Reduction of Ortho-Nitro-Benzoic
Acid to Anthranilic Acid
E. W. Pfafflin and E. F. Winter
PRESIDENT AND FACULTY
ARMOUR INSTITUTE OF TECHNOLOGY
FOR THE DEGREE OF
BACHELOR OF SCIENCE
MAY 31, 1921
ILLINOIS INSTITUTE OF TECHNOLOGY ^ ^ ^^^i^^s^.^^^ ^.^.^
PAUL V, GALViN LIBRARY ^^/7/?/ t fi<:,-^.^^ ^^ ^
36 WEST 33RD STREET '^-
Dean of Cultural Studies
Digitized by tine Internet Arciiive
in 2009 witii funding from
CARLI: Consortium of Academic and Researcii Libraries in Illinois
Ao knowledgment .
Theory of the Proced-ure,
Realizing that oiir work has only tonchsd
on this inportant problem and hoping that it will
"be solved in the near ±\iture by more competent
scholars of chemistry, we wish to exj.)ress our
appreciation for the time and effort given iis by
rrofessor Harry McCorrnack, head of the Chemical
Engineering Department, -irmour Institute of
Technologj'-, Chicago, Illinois.
iieduction is the name usually given to a
reaction in v/hich oxygen is withdrav.-n fron, or
hydrogen added to a conpound. In certain cases
"both of these processes occur.
In a preliminary study of reducing agents
we find that reduction can he accomplished in a
nunher of ways:- Has cent hydrogen in acid,
neutral and alkaline solution is the most common,
although it has not met with great success as a
reducing agent for organic compoxmds. "^lOdiran and
sodium amalgam are very efficient and may he applied
conveniently. Metallic tin and stannous chloride
are also used extensively. i;inc and zinc dust can
"be used in either acid or alkaline solutions, and
at times if necessary in neutral sol-ations.
it is well loiown that reduction converts IIO
into EH . The agents mostly employed for the
reduction of nitro compounds are tin and
hydrochloric acid. The advantage of these bodies
is the ease of separating the tin by hydrogen
sulphide; in the solution there remains only the
chloride of the amino compounds. The amines with a
basic ciiaracter are precipitated froE their
acid solutions by ammonia; amino-phenols , by
sodium carbonate; anino-earboxylic acids, by
THEORY OF THB PROCEDURE .
The reduction oi" the ortho-nitro-bensoic
acid is the removal of the oxygen in the nitro
group and the substitution of hydrogen in its
place to form the amino group. The structural
formula of the basic reaction is as follows--
To accomplish such a reduction reaction, it
is necessary to use some metal which on addition
to potassium hydroxide will liberate nascent
hydrogen. v;e found that various metals were
capable of such action.
The second reaction in this v;ork would be
the removal of the metal from the solution. i'Tora
the properties of the reduced solution and also
of the metal, v;e found the sulphides were
insolu'ble in alkaline solution, and also tliat
the reduced ortho-nitro-benzoic acid v;as
soluble even in the presence of the sulpiiide.
T'he metal sulphide precipitate filtered leaves
tbe reduced ortho-nitro-benzoic acid in
'[■he third reaction in this work is to
obtain some kind of solution in which the
reduced ortho-nitro-bensoic acid is less soliible
than that of the material used to precipitate it.
A salt of copper seem.s to be the most
adaptable to this purpose for tv/o reasons:- One
that the reduced ortho-nitro-benzoic acid is less
soluble in such a solution than is the salt of
copper, and second that the copper can be removed
from the solution by the addition of HpS, forming
an insoluble precipitate of copper sulphide which
can be filtered off, This should leave the reduced
ortho-nitro-benzoic acid, or the ortho-amino-
benzoic acid, or better named Anthranilic acid in a
solution in v/hich it can be recrystallized.
Anthranilic acid can be re crystallized from
vmter solution, and its purity determined "by its
properties and its melting point.
Anthranilic acid is solnble in ether,
alcohol, and v;ater, to the greatest extent in the
former v/hich is the only solvent fror, v/hich it
will crystallize in long needles, the other solvents
yielding a granular product. It crystallizes in
leaflets v-hich melt at 144-5° G. The aoueous
solution shovi's a hlue fluorescence and tastes sv/eet.
Our prohlem. is to find a cheaper and more
easily conductahle method for the production of
snythetic indigo from ortho-nitro-toluol. The
process has already "been carried to ortho-nitro-
"benzoic acid hy the oxidation of ortho-nitro-toluol.
Our work in the main is to reduce this ortho-nitro-
"benzoic acid to ortho-amino-henzoic acid by a simple
and ine:q)ensive procedure. The anthranilic acid can
then he easily converted into indigo "blue.
The reaotions are as follov/s:-
O'-yMAff^^^'^^l^^'^ CuS^AO/puJUo O/i^
At the present time processes for
synthetic indigo have, "by the application of
scientific knovvledge and of untiring efforts,
"been worked out "by German chemists, "by v/hich it
is possible to produce indigo "blue on a large
scale and at a small profit.
The process is carried out, as is indicated
b7/ the eqtiations.
Thjs would not he a satisfactory process
in this country for the reason that the materials
used are expensive and the process requires skilled
lahor and considerahle time.
The nit ro- compounds are reduced "by nascent
hydrogen in acid, alkaline and neutral solutions.
?or the reduction of each nitro group six atoms of
nascent hydrogen are necessary and the reaction
may be e:>rpressed as follows :-
aiOg -f- 6H — ►UIHg -+- 2H„0
The amine produced comhines with excess of
acid to form a salt, e.g. XEffl HCl, from which the
amine is obtained by the addition of an excess of
caustic alkali. Tin and hydrochloric acid are
usually employed, the metal being first converted
into stannous and then into stannic chloride. The
complete reaction is as follows :-
2i:ii0^+ 3Sn-M4HGl — ^SfZ.lfflg.HCl) -h3SnCl4+4H
The hydrochloride of the amine combines with
the stannic chloride, forming a stanni chloride
(RMgHGl)SnCl^. Various methods are adopted in order
to obtain the free amine from the acid mixture.
In this case it is necessary to precipitate the tin
from the diliited acid solution by means of hydrogen
sulphide. The stannous or stannic sulphide is
separated by filtration, the amine hydrochloride
subsequently decomposed with alkali, and the free
amine extracted with ether.
The objection to this method v;e found was the
fact that the ortho-nitro-benzoic acid was only
slightly soluble in acid sol-ution and therefore a
corresponding lovi? yield of anthranilic acid could
Alkaline solution also favors reduction,
and since the ortho-nitro-henzoic acid is soluble
in such solutions, it was used.
Mechanical stirrers were used to keep the
solution of ortho-nitro-benzoic acid, potassium
hydroxide, and the metal in constant agitation.
jj'or the evaporation of the reduced solution
of ortho-nitro-benzoic acid, to concentrate and
crystallize the ortho-amino-benzoic acid, a vacuum
drier was used. This was a steam heated oven
connected with a centrifugal pump to exhaust the
air. This pump rxmning under normal conditions v/as
capable of maintaining a twenty five and one half
Most of the equipment used in this work was
standard labratory equipment, such as sand bath,
drying oven, hydrometers, funnels, beakers and test
To reduce the ortho-nitro-benzoio acid, it
was evident that the process was one which required
the removal of the ozygen and the addition of the
hydrogen, xieduction with hydrogen can he
accomplished only when the hydrogen is in the nascent
state. Molecular hydrogen will not afford reduction.
We found that nascent hydrogen can also he generated
in acid, alkaline, or neutral solutions; so our first
problem was to determine the solubility of the ortho-
nit ro- "benzoic acid in acids, alkali, water and alcohol.
The acids used were those which will liberate
nascent hydrogen on the addition of some metal,
namely: hydrochloric, sulphuric, acetic, and other
organic acids, we found that the ortho-nitro-benzoic
acid is almost insoluble in any of the acids named.
Mve grams of the ortho-nitro-benzoic acid v/ere added
to 100 c.c. of n/10 ECl. The solution was agitated
for a period of one hour. The acid was then diluted
and evaporated almost to dryness. The residue taken
up with hot water and the ortho-nitro benzoic acid
recrystallized. 4.78 grams of the acid were recovered
or 95.3070. The results with the other acids were
somewhat unsatisfactory particularly the organic
acids. We fo-und later that addition compounds of
the acids were formed.
The alkali used in the testing of the
solubility was potassium hydroxide. (Potassium
hydroxide was used in place of sodium hydroxide,
"because of the inability of the storeroom to
supply the latter). The ortho-nitro-henzoic acid
was readily soluble in the alkali which did not
necessitate the determination of the degree of
Water was also tested but close observation
was sufficient to report that the acid v/as not
soluble in the water.
Conclusions from- the tests on solubility
and the results which have already been obtained
and recorded in handbooks, we decided that the
reduction reaction which we wished to make would
have to be made in alkaline solution.
oince the potassium hydroxide proved to be
the best solvent for the ortho-nitro-benzoic acid,
and also because it was possible to produce nascent
hydrogen in such a solution, we next proceeded to
determine whether alkali of different concentration
varied the soluljility. The result v/as obvious; the
stronger the alkali the more soluble the acid,
iiowever, we found later that the concentration of
the alkali varied the yield of the addition compounds
formed. The results of this experimenting proved
that 5° jjaume potassium hydroxide gave the best
yields of addition compounds of anthranilic acid.
The next problem was the selection of a
metal which would produce nascent hydrogen. Zinc
and aluminum were the metals selected to afford the
liberation of hydrogen for the reduction. It v/as
evident at the outset that each of these metals
v;ould produce the required results, but
complications which arose later limited the selection.
The aluminiffii proved unsatisfactory because of two
reasons: one that the aluminum became coated with
a film of oxide which prevented trie further
liberation of hydrogen; and second we found it
impossible to secure any suitable means of removing
the aluminum from the solution after the reduction
had been completed.
The metal zinc was then 1186(3. in the
granular state because of its ability to
liberate the hydrogen and also because an easy
and efficient method for its removal from
solution was known. Ciuantative runs proved that
very little of the zinc entered the solution,
ciamples of 5 grams of the ortho-nitro-benzoic acid
was dissolved in 125 o.c. of the 5° Baume potassium
hydroxide and 2 grams of the granular zinc added.
Also 2 grams of the zinc was added to 125 c.c. of
5° i3aume Potassium hydroxide v/ith the absence of
the ortho-nitro-benzoic acid. The two solutions
were agitated for two hours after which reduction
was complete in the one case and in the second all
the potassium zincate was formed that the reaction
called for. The solutions were then heated to
about 85° 0. and allov/ed to absorb HpS under a
pressure of two inches of water for one hour. The
precipitate of zinc sulphide was filtered off, dried
and vreighed as zinc siilphide. rhe results shov^^ed
that almost equal amounts of zinc entered the two
solutions. This part of the work was only carried
on in order to make a rough estimate of the quantity
of zinc which it would be necessary to remove if
the method proved one of commercial importance.
iJo effort was made on the part of the
experimenters to prevent the zinc from entering
the solution "because of the ease with which it
could he removed in the experimental v/ork. It may
have been necessary to obtain such a procedure, had
the results of the thesis "been positive.
The numerical results were as follows:
In the solution of ortho-nitro-benzoic 66.23% of
the original zinc was precipitated in the form of
zinc sulphide from the zincate solution.
Zn 2K0H ^2 ^^^2 ^^
KgZnOg E S ZnS 2K0H.
62.50% of the zinc was recovered from the second
sample which did not contain the ortho-nitro-benzoic.
Whether the ortho-nitro-benzoic acid favored the
solubility of the zinc, or whether it was an error
on the part of the experimenters, was not determined
because the item carried little weight.
The next problem which confronted us was to
make the solution from which the zinc had been
extracted, one in which it would be possible to
crystallize the acid which we were looking for.
This proved to he the most difficult prohlem in
that anthranilio acid has a great affinity for
nearly all metal salts, rhe proof of this
conclusion rested wholly in the salt formed v.'ith
nlokel sulphate, upon the addition of nickel
sulphate to the solution of anthranilio acid, we
found that it was impossible to obtain a
precipitate of nickel sulphide, because of the
inability of the nickel to ionize in such a
We also found that it was possible to
obtain solutions with other acids which would
render the anthranilio acid less insoluble.
Great care was exercised in the evaporation of the
resulting solutions because of the tendancy of the
organic acids to form addition and substitution com-
pounds, and tar. iror this reason we found that it
was necessary to evaporate the solutions under
reduced pressure and at a low temperature so that the
product would not go to tar or be burnt. The vacuum
oven described in the paragraph on apparatus, was
used for this purpose.
Among the aoids whioh were used to
precipitate the anthranilio acid were citric,
acetic, oxalic, tartaric, and hydrochloric.
With the addition of the citric acid no
precipitate was formed, we drew a conclusion
from this that the citric acid formed an addition
compound vdth the anthranilic acid which was
soluble. The addition of oxalic, tartaric, and
hydrochloric acids gave similar results. Y/hen
acetic acid was added to the solution, a
precipitate was obtained. This precipitate was
washed from the filter paper and dissolved in v/arm
water, and allowed to evaporate in the vacuum oven.
The resulting material was of a spongy amorphous
nature, yellow in color and having a melting point
of 198.5° Centigrade. An analysis was not necessary
to prove its composition, however to obtain the
satisfaction that the product was an addition compound
of acetic and anthranilic acids or acet-anthranilate ,
the follovYing method was employed: A small portion
of the material was mixed with an equal proportion of
crystals of phosphoric acid. It was then diluted
with water and distilled in a distilling flask.
condensing the vapor in a water cooled condenser.
The theory of this operation was that the phosphoric
acid "being a stronger acid than the acetic v;ould
replace the acetic, changing the acet-anthranilate
to phosphoric-anthranilate. This would liberate the
acetic acid and allow it to he distilled over into
the receiving flask. This distillate can be tested
for the presence of acetic acid by some of the
standard methods. I'he one which was employed by the
experimenters was a physical property, namely the
vie found that acetic acid was present in the
distillate proving the aforesaid statement, that the
addition of the acetic acid to the solution of
anthranilic acid forms an addition compound, i^o
suitable means was at hand to separate the addition
compound formed so the method was discarded. The
addition of the other acids v;ould have presented the
same difficulty had v^^e tried to isolate the soluble
addition compounds formed.
After consulting the literature again we
found that the real problem in the thesis was the
separation of anthranilic acid from the salts used
to precipitate it. Because of the small amoiuit of
material in the literature, this subject was not
touched upon so the experimentors decided to find a
metal salt which would not form an addition compound
and also allow the anthranilio acid to crystallize
from the solution.
Anthranilio acid was prepared "by the
phthalimide method, as described in the introduction.
The product was tested for its purity and determined
to he 98. 3^^ pure. The melting point of the product
was 145° C. The melting point of the acid given in
the handbooks is 144° C.
(Hote ) . All of the melting points determined in
this work and mentioned in this experiment were
determined as follows:- A small portion of the
material was ground to a fine pov;der and inserted in
a capillary tube. The tube was then fastened to a
thermometer so that the bulb of the thermometer and
the bottom of the capillary tube were at the same
level. This was then immersed in two beakers of
sulphuric acid, one beaker set inside of the other
to assure an equal temperature of the acid. Heat
was then applied to the "beakers, and the acid kept
thoroughly agitated until the material in the
capillary tuhe melted. This point can readily be
seen hy the observer and the temperature also noted.
I'he anthranilic v;as first tested to determine
from which solvent it would crystallize best. Alcohol,
ether, and water were used as solvents, we found
that the acid crystallized readily from ether and
alcohol, but not so readily from water. Later,
difficulties arose which prohibited the use of
alcohol and ether, so the experimenters were forced
to use water, however we found it very easy to
reorystallize the anthranilic acid,
A small quantity of the acid 7/as then dissolved
in ?/ater and the following salts were added to each
of 12 small portions of the anthranilic acid. The
solutions were then heated and allowed to absorb
HgS under a pressure of two inches of water for a
period of one hour.
Copper nitrate was added giving a precipitate
of copper-anthranilate of blue color. HpS was then
passed and the precipitate blackened in color.
supposedly that of GuS. The precipitate was
filtered off and the filtrate evaporated to
dryness in the vacuiun oven. The residue was a
yellow crystalline mass trndouhtedly an addition
compo-und of copper anthranilate. The melting
point was found to "be 219*^ C.
Silver nitrate was added giving a "black
precipitate of silver anthranilate. HpS was then
allowed to pass through the solution for one hour
at a pressure of two inches of v/ater. There was
no vlsahle change in the nature of the precipitate
"but it was supposed and afterwards proven that the
silver precipitate was AggS. The filtrate was
allowed to evaporate in the vacuum oven which left
a dirty yellow mass, amphorous in structure and
having a melting point of 223° C.
Lead- nitrate was next employed, giving a
white precipitate. Upon the addition of H S the
white color turned black. The solution was filtered
and the filtrate evaporated as before. The residue
this time was brown having a crystalline form and
melting at 220° C.
Mercuric nitrate also gave a precipitate
white in color, which upon the addition of the
H„S darkened considerahly. This was likewise
filtered and the filtrate evaporated as before.
This tiiBe a white crystalline mass resulted which
v/hen tested for its melting point gave 232° C
P03TI0N 5 .
Baritun was the last of the nitrates to he
tested for its ability to form addition compoxmds
with the aathranilic acid. For some unknown reason
no precipitate v/as formed on the addition of the
barium salt and on the addition of the H2S only
sulphxjr was precipitated. Results discarded.
C0I^CLU3I0ITS li^avl glHST ITiyE PCHTIOES .
The salts used in portions 1 to 4 inclusive
gave only addition compounds, while 5 seemed to have
no affect whatsoever on the acid solution.
Barium chloride v;as next added to the
anthranilic acid solution. This salt behaved as
did the barium nitrate but when the HgS was passed
a precipitate was formed unliice the one formed
in the case of sample 5. The precipitate was
filtered off and the filtrate evaporated. The
result of this salt was a positive one in that the
residue left in the evaporating dish resembled
the anthranilic acid v/hich we had started with,
and v;hich also had a melting point of 14 6° G,
Believing that for some unJaiov/n reason this salt of
barium might behave different under different
conditions, experimenting was not stopped at this
Because of the inspiring results obtained
when the chloride was used, and also from the
amount of information vfcich v;e had found in the
literature concerning the salt of copper we decided
to use copper chloride. Copper anthranilate
precipitated very nicely, and changed color upon
the addition of the HgS , but to no avail. '.Then the
precipitate was filtered and the filtrate allov;ed
to evaporate in the vacuum oven only a resinous
tarry mass v;as left.
Another ahloride was used namely the
merctacic chloride. This was likewise added to
the solution of anthranilic acid. A white
precipitate was formed which turned black upon
the addition of the HgS . This v/as filtered and
the filtrate evaporated to dryness in the vacuum
oven. The crystalline roass which remained proved
to be anthranilic acid having a melting point of
This sample was tested by the addition
of aluminum sulphate, but was rapidly discarded
because of the condition of the aliiminum
precipitate, which rendered it almost unfilterable .
■Jhen nickel sulphate was used we found
results v/hich were very much out of the ordinary.
Nickel anthranilate precipitated, but upon the
addition of HpS no further change took place.
This was readily observable because the color of
the nickel anthranilate was green, and upon
the addition of HpS it did not turn black, v/hich
is the color of the HiSg. This proved that the
nickel anthranilate does not ionize as a nickel
salt and could not "be precipitated "by the use of
Zinc sulphate was the salt added to this
sample "but no precipitate v/as formed either on
the addition of the ZnS04 or on the addition of
the HgS. Evaporation of the solution resulted in
a tarry mass.
xiead suhacetate was lastly used in the
attempt to recrystallize the acid from solutions
of salts. The result in this case was an
amorphous yellow mass which melted at approximately
GOICLUSIO^S gROM SMIPLBS 6 to 12 .
Samples 6 and 8 were the only ones which
anthranilic acid could he recovered from.
Samples 7,9,10, 11, 12. were discarded for
the various reasons named.
The results from the anthranilic recrystalliza-
tion only lend additional problems in this work.
Conditions may have altered the results
materially, "but ov/ing to the niunlDer of addition
compounds formed we deemed it unnecessary to try
such a thing as a quantitative run. The size of
the addition compounds or rather the hulk of them
was sufficient evidence for us that addition
compounds were the only things we had thus far
jfTom the results on the escperimenting just
descrihed, we proceeded from the original basis
namely the reduced solution of ortho-nitro-
"benzoic acid, using all of the data obtained from
the experimenting on the anthranilic.
jPROGEDURS ETOMBSR 1.
A 5 gram sample of ortho-nitro-henzoic acid
was dissolved in 125 c.c. of 5° Baume potassium
Case A. The solution was boiled before agitating.
Case B. The solution was agitated with no boiling,
£ grams of granular zinc was also added to each
J?R0C2DUHE UUMBSH 2.
The solution was decanted, boiled and
allov/ed to absorb HgS for a period of one hour
■under a pressure of two inches of water. The
solutions were heated again if the temperature
fell "below 80° U. The precipitate which was
formed was filtered off, which when tested gave
positive results for zinc sulphide.
PROCEDURE UMBER 3.
Ihis is where the process tranches, hecause
of the addition of different salts to favor the
crystallization of the ortho-amino-henzoic acid.
The 5 gram sample of the ortho-nitro-
l)enzolc acid was treated as in procedure 1, case B,
and procedure 2, In procedure 3, acetic acid was
employed. Dilute acetic acid v;as added to the
solution until it showed an acid reaction v;ith
phenophthalein, when this point was reached a yellow
precipitate was formed. The precipitate was washed
from the filter paper and dissolved in a small
quantity of hot water, evaporated in the vacuum oven
and re crystallized from water. The resulting residue
was an amorphous spongy yellow mass similar to that
ohtained when acetic acid was added to the solution
of anthranilic acid. The melting point of this
hody was 201° G.
SlIdPLES n and m.
These were also 5 gram samples of the
ortho-nitro-benzoic acid, treated as in
procedure 1, case A and B, and procedure 2. Both
samples, the one which had been boiled and the
one which was allowed to react without the aid of
heat, were treated as follows:- copper acetate
was added, giving the precipitate of copper
anthranilate, as it did in the case of the
solution of anthranilic acid. HgS was then passed
into both of the solutions and the precipitate of
copper sulphide filtered off. The filtrate was
evaporated in the vacuum oven under a reduced
pressure of £3,5 inches of mercury and at a
temperature of 68° C. Both of the samples gave a
yellow amorphous mass which was dried and treated
with carbon bisulphide to remove the sulphur. This
caused the mass to change color from the original
yellow to a dirty white, i'he melting point of
both of these products was about 187° C.
SAMPLES IV. V, VI, Vll, Vlll.
These samples were treated as in procedure
1-B and 2, and the following salts were added:
IV Sodium acetate.
"V lead acetate.
VI Zinc acetate
VII Lead suhacetate.
VIII Ammonium acetate.
aample IV was discarded because of the
tarry residue which was left upon evaporation.
Sample V was re crystallized from water
and the product tested for its melting point.
Sample VI was discarded because there was
no precipitate upon the addition of the zinc
Sample Vll was carried through by the
regular procedure but the product showed a melting
point of 200° G.
Sample Vlll was discarded because of the
failure to precipitate upon the addition of the
The following salts which were employed were
either used "because positive results had "been
ohtained from the saithranilic acid experiments
or he cause of the property of the salt to form
addition compounds with the anthranilic acid.
We thought it necessary to use such salts as
those which had formed addition compounds, to
prove that the ortho-nitro benzoic acid had teen
reduced hy the process to which it had "been
Copper nitrate was used to precipitate the
anthranilic acid. After the removal of the copper
hy the addition of the iipS the filtrate was
evaporated and the residue tested for anthranilic
acid. The melting point of the product was 215° C.
which was only 4° from the melting point of the
product obtained when the copi:)er nitrate was added
to the solution of anthranilic acid. It was
extremely hard to get this compound, i'ive such
samples v;ere run, four of v/hich resulted in only a
tarry resinous mass.
Lead nitrate was next used in an effort to
obtain the pure anthranilic acid, when the nitrate
was used in experimenting v/ith the anthranilic
acid, an addition oompoimd was formed whicTi
melted at 223° C. Five such samples were used
in this effort "but each of the five times only a
tarry mass remained in the evaporating dish after
evaporation, xemperature as low as 60° C. were
employed to try and prevent the organic compounds
from turning to tar, hut v;ith no result.
Barium chloride was one of the salts which
had permitted the anthranilic acid to recrystallize
when added to a solution of the acid. Extreme care
was taken in the evaporation of the filtrate so as
to prevent, if possihle, the formation of tar. In
this case the solution Y/as evaporated and left a
crystalline mass of yellow material. This was re-
dissolved in a small amount of hot water and
re crystallized. The product looked as though we had
found the suitable salt, hxit the melting point of the
product, instead of heing 144-5° C. as is that of
anthranilic, was 210° C,
copper sulphate was added to this sample.
The solution was carried through the same
processes as were the others. The residue was a
hrown crystalline mass melting at 219*^ C.
Zinc sulphate gave approximately the same
results as did the copper sulphate.
Mercuric chloride, one of the salts which
had also allowed the anthranilic acid to
re crystallize was used, rhe sample was carried
through the same procedures as were those in the
ahove cases. The residue was recrystallized from
water solution hut to no avail. The melting point
was found to he 197° G. The melting point when the
mercuric chloride was added to the solution of
anthranilic acid was 146° which is somewhat near the
melting point of anthranilic acid.
Since all of the ahove methods failed in some
way or other, the experimenters decided to try some
of the other methods used in organic chemistry for
the separation of the metal from the salt, i'hese
methods did not offer a very wide field due to
various reasons, with the use of acid to
precipitate calcium or "barium, only addition
compounds would he formed and with the second
possibility that the organic material would he
reduced to tar. baits of "barium and calcitan were
used, however, and an effort made to precipitate
them from the solution hy the passage of carhon
dioixide under a pressure of 2 inches of water.
Conditions of temperature were varied and also the
time of absorption, hut the precipitate formed
could not he readily filtered. It was evident
at the outset from our Icnov/ledge of quantative
chemistry that either of these precipitates would
he hard to handle.
From the results of all of the experimenting,
it follows that the ortho-nitro-henzoic acid was
reduced in alkaline solution hy nascent hydrogen
produced by the action of granular zinc on
potassium hydroxide. We can draw this conclusion
from the facts that copper nitrate when added to a
solution of anthranilic acid gave an addition
compoimd which resemhled and melted fotir degrees
from the addition compound formed when the copper
salt was added to the reduced solution of ortho-
nitro-henzoic acid, .-e also found that no heat
was necessary for this reduction, however, heat
was generated to a small extent in the reaction.
Even though the reduction can "be
accomplished we are forced to draw the conclusion
that anthranilic acid cannot be made by this
process because no suitable means was found that
will successfully separate the acid from its salt.
It is also evident that anthranilic acid has a strong
affinity for most acids and metals, thereby
rendering it difficult to obtain it in the free state.
It may be possible hoYi^ever to make indigo blue
without first obtaining the free anthranilic acid
by forming the chloracetic addition compound which
is really the intermediate product between
anthranilic acid and indigo blue.
General iTinciples of Organic Chemistry Alexoyeff.
Praotioal Organic Chemistry. Sudburough and James.
Organic Chemistry. Perkins and Kipping.
Organic chemistry. lloyes.
Organic Chemistry. Kichter.
Jahreshuoh iiaurent 589.
Berichte 19 1402
Aunalen 39 91
Annalen 39 83
Beilstein, Kuhlberg, Ihig 163. 138.
Journal Chemical Society 37
Hoogenwerf, Van Dorp, liec, trav, chim, Pays - Bas 10